Aim: Autosomal dominant polycystic kidney disease (ADPKD) is a common genetic disease that progresses to end-stage renal disease (ESRD). Tolvaptan is a disease-modifying agent that slows cyst growth and kidney disease progression in ADPKD. In this study, we examined the effects and side effects of tolvaptan in high-risk ADPKD patients using tolvaptan. We share our experience of this study. Methods: Twenty-seven ADPKD patients who were at high risk according to the Mayo Clinical Classification and accepted treatment were included in the study. Tolvaptan 60 mg/day orally was started in patients to slow the ADPKD. The daily dose was increased to 120 mg depending on the patients’ response to tolvaptan treatment and their tolerance to side effects. The patients were followed up during tolvaptan treatment to observe the effects and side effects of the medication. Results: The mean age of the patients was 40.3±8.2. Hypertension was present in 81.5% of the patients, and they mostly used renin angiotensin aldosterone system inhibitors. As aquaretic side effects of tolvaptan treatment, there was thirst in 14 patients (51.9%), polydipsia in 10 patients (37%), dry mouth in 5 patients (18.5%), and nocturia in 4 patients (14.8%). In addition, although liver enzyme elevation, hypernatremia, and acute kidney injury were observed in one patient each, these side effects did not lead to permanent discontinuation of the drug. Polyuria was observed in all patients, but the patients tolerated the polyuria well and continued to use tolvaptan treatment. Conclusion: Although the patients experienced side effects related to tolvaptan treatment, none of the patients discontinued the drug permanently. We observed that patients generally tolerated tolvaptan treatment well.